Among all the data storage solutions, the optical discs are becoming more and more important for backing up data and exchanging information because the optical storage media have many advantages including a high storage capacity, easy to handle, and a long preserving time for the stored data. The optical disc drive also becomes more popular for this reason, and there are many types of the optical disc drive being provided for different users such as H/H type, slim type, slot-in type, and so on. Till now, the optical disc drive of slot-in type can be found all around such as notebook or laptop computers, DVD players, and even some instruments or electronic products with built-in microprocessors.
Referring to FIGS. 1 to 3 partly exploded and bottom views of a conventional disc drive of slot-in type are shown. The conventional disc drive includes a casing (not visible) having a front wall formed with a disc entrance-and-exit slot 10, a mounting frame 1 enclosed by the casing, a disc transport mechanism disposed in the casing adjacent to the entrance-and-exit slot 10 and mounted on the frame 1, and four positioning pillars 1a, 1b, 1c, 1d. The disc transport mechanism 6 includes a transport roller 6 journal led movably on the mounting frame 1, a pair of front disc-guiding members 101 disposed adjacent to the entrance-and-exit slot 10, and a pair of rear disc-guiding members 102 disposed distal from the entrance-and-exit slot 10. Each of the positioning pillars 1a, 1b, 1c, and 1d is attached to a respective one of the disc-guiding members 101, 102. Upon detecting presence of an optical disc 9 near the entrance-and-exit slot 10 in the casing, the transport roller 6 is actuated to rotate in a first direction in such a manner to push due to applying force on the optical disc 9 inward via the entrance-and-exit slot 10 against biasing action of the disc-guiding members 101, 102. The periphery of the optical disc will abut and push the front and rear disc-guiding members 101, 102 to a temporary position within the casing. The disc 9 is retained temporarily at the temporary position and is later conveyed to a reading position, where the disc 9 is disposed securely onto a rotating seat 2 with the assistance of a clamp 4 (see FIG. 5). At the reading position, a gap “g” needs to be formed between the disc 9 and the positioning pillars 1a, 1b, 1c, 1d (see FIG. 6) to permit smooth rotation of the disc 9.
Note that, in the conventional disc drive, each of the pillars 1a, 1b, 1c, 1d has a uniform width throughout the axial length. In order to provide the gap “g” between the positioning pillars 1a, 1b, 1c, 1d and the disc 9 when the disc is moved to the reading position, it may sacrifice the precision of positioning an optical disc onto a rotating seat. Under this circumstance, when the disc 9 is moved to from an exterior of the casing into the temporary position, the periphery of the disc 9 may not be coaxial with the rotating seat 2 (see FIG. 2), which in turn can result in improper positioning of the disc 9 on the rotating seat 2 when the disc 9 is moved to the reading position from the temporary position.